Lipids, owing to their water insolubility, require a variety of fatty acid binding protein (FABP) chaperones or transporters to carry them throughout cells (Furuhashi, M et al. 2008). The FABPs are part of the pathway of anandamide inactivation by the fatty acid amide hydrolase (FAAH), an enzyme localized inside the cell on the endoplasmic reticulum. The endocannabinoid anandamide (arachidonoyl ethanolamide or AEA) is an uncharged neuromodulatory lipid that is inactivated through its cellular uptake by FABPs and subsequent hydrolysis by FAAH into ethanolamine and arachidonic acid.
Cannabinoids such as anandamide have broad effects on the central nervous system (CNS) and influence, for example, movement, memory, nociception, endocrine regulation, thermoregulation, sensory perception, cognitive functions, and mood. Similarly, genetic and pharmacological studies have revealed a broad role for endocannabinoid signaling in a variety of physiological processes, including neuromodulator release, motor learning, synaptic plasticity, appetite, and pain sensation. Anandamide produces most of its pharmacological effects by binding and activating the cannabinoid receptor (CB-1 and CB-2) within the CNS. The increase in extracellular anandamide caused by the inhibition of FABPs triggers activation of the cannabinoid receptor type 1 (CB-1) pathway leading to the relief of neurogenic and inflammatory pain.
Recently, it was shown that anandamide (an endocannabinoid) uses FABPs such as FABP5 (E-FABP) and FABP7 (B-FABP) as intracellular transporters (Kaczocha, M. et al. 2009). FABPs are drug targets similar to FAAH since inhibitors of each decrease hydrolysis of anandamide and its uptake into cells, raising the levels of extracellular anandamide (FIG. 1) (Howlett, A. C. et al. 2011; Kaczocha, M. et al. 2012; Ahn, K. et al. 2009). Few specific FABP inhibitors have been described. There are those that were specifically designed for FABP4, such as BMS309403, which are important for the protective effects that they exert in metabolic syndrome and atherosclerosis (Barf, T. et al. 2009; Sulsky, R. et al. 2007). BMS309403 also binds other FABPs, such as FABP5 and FABP7, that carry anandamide, as do other inhibitors originally designed to inhibit a putative anandamide transmembrane transporter (Kaczocha, M. et al. 2012).